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排序方式: 共有43条查询结果,搜索用时 5 毫秒
1.
2.
Walters JR Barley NF Khanji M Rhodes-Kendler O 《The Journal of steroid biochemistry and molecular biology》2004,(1-5):317-319
Intestinal absorption of dietary calcium is regulated by 1,25-dihydroxycholecalciferol (1,25(OH)(2)D(3)) in humans and in experimental animals but interspecies differences in responsiveness to 1,25(OH)(2)D(3) are found, possibly due to differences in the promoters of genes for intestinal calcium transport proteins or of the Vitamin D receptor (VDR). The epithelial calcium transporter, known as ECAC2 or CAT1, the product of the TRPV6 gene expressed in proximal intestinal enterocytes, is the first step in calcium absorption and studies in mice have shown that its expression is Vitamin D-dependent. In contrast in man, we showed that duodenal TRPV6 mRNA expression was independent of blood 1,25(OH)(2)D(3), although in Caco-2 cells, 1,25(OH)(2)D(3)-dependent changes have been demonstrated. We sought to explain these findings. A consensus Vitamin D response element in the mouse gene is absent in the human gene. We re-analysed our duodenal expression data according to a CDX2-site polymorphism in the VDR promoter. Mean TRPV6 expression was the same, but there was evidence of different responsiveness to 1,25(OH)(2)D(3). In the GG genotype group, but not the AG, duodenal TRPV6 expression increased with 1,25(OH)(2)D(3). We postulate that lower levels of expression of VDR in the GG group produce greater sensitivity to 1,25(OH)(2)D(3). 相似文献
3.
4.
Anthony J. Barley James E. Cordes James M. Walker Robert C. Thomson 《Molecular ecology》2022,31(1):266-278
Unisexual vertebrates typically form through hybridization events between sexual species in which reproductive mode transitions occur in the hybrid offspring. This evolutionary history is thought to have important consequences for the ecology of unisexual lineages and their interactions with congeners in natural communities. However, these consequences have proven challenging to study owing to uncertainty about patterns of population genetic diversity in unisexual lineages. Of particular interest is resolving the contribution of historical hybridization events versus post formational mutation to patterns of genetic diversity in nature. Here we use restriction site associated DNA genotyping to evaluate genetic diversity and demographic history in Aspidoscelis laredoensis, a diploid unisexual lizard species from the vicinity of the Rio Grande River in southern Texas and northern Mexico. The sexual progenitor species from which one or more lineages are derived also occur in the Rio Grande Valley region, although patterns of distribution across individual sites are quite variable. Results from population genetic and phylogenetic analyses resolved the major axes of genetic variation in this species and highlight how these match predictions based on historical patterns of hybridization. We also found discordance between results of demographic modelling using different statistical approaches with the genomic data. We discuss these insights within the context of the ecological and evolutionary mechanisms that generate and maintain lineage diversity in unisexual species. As one of the most dynamic, intriguing, and geographically well investigated groups of whiptail lizards, these species hold substantial promise for future studies on the constraints of diversification in unisexual vertebrates. 相似文献
5.
An effect of vitamin B 12 deficiency in tissue culture 总被引:1,自引:0,他引:1
6.
Jennifer A. Learmonth Sinead Murphy Patricia L. Luque Robert J. Reid I. Anthony P. Patterson Andrew Brownlow Harry M. Ross Jason P. Barley M. Begoña Santos Graham J. Pierce 《Marine Mammal Science》2014,30(4):1427-1455
Life history parameters were determined for stranded and bycaught harbor porpoises (Phocoena phocoena) from Scottish (UK) waters (1992–2005). Fetal growth rate was 84.4 mm/mo and mean size at birth was 76.4 cm (range 65–88 cm). Males and females had a similar range of body lengths (65–170 cm and 66–173 cm, respectively), although asymptotic lengths were higher in females than males (approximately 158 cm and 147 cm, respectively). Nonpregnant females were significantly lighter, in relation to their length than males. Maximum estimated age was 20 yr for both sexes. Age at sexual maturity (ASM) was estimated as 4.35 yr in females and 5.00 yr in males. Conception occurred mainly in July and August although reproductively active males were recorded during April to July. Gestation lasted 10–11 mo, with calving mainly between May and July. Lactating females were recorded during June to November, while small calves with solid food in their stomachs were found mainly during February to May. Estimated pregnancy rate (0.34–0.40) is lower than recorded elsewhere, but is likely underestimated due to the prevalence of mature females of poor health status in the sample. Nevertheless, cetacean strandings can be an essential source of data on demographic parameters. 相似文献
7.
L. A. Marquez-Cedillo P. M. Hayes B. L. Jones A. Kleinhofs W. G. Legge B. G. Rossnagel K. Sato S. E. Ullrich D. M. Wesenberg North American Barley Genome Mapping Project 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2000,101(1-2):173-184
Characterization of the determinants of economically important phenotypes showing complex inheritance should lead to the more
effective use of genetic resources. This study was conducted to determine the number, genome location and effects of QTLs
determining malting quality in the two North American barley quality standards. Using a doubled-haploid population of 140
lines from the cross of Harrington×Morex, malting quality phenotype data sets from eight environments, and a 107-marker linkage
map, QTL analyses were performed using simple interval mapping and simplified composite interval mapping procedures. Seventeen
QTLs were associated with seven grain and malting quality traits (percentage of plump kernels, test weight, grain protein
percentage, soluble/total protein ratio, α-amylase activity, diastatic power and malt-extract percentage). QTLs for multiple
traits were coincident. The loci controlling inflorescence type [vrs1 on chromosome 2(2H) and int-c on chromosome 4(4H)] were coincident with QTLs affecting all traits except malt-extract percentage. The largest effect QTLs,
for the percentage of plump kernels, test weight protein percentage, S/T ratio and diastatic power, were coincident with the
vrs1 locus. QTL analyses were conducted separately for each sub-population (six-rowed and two-rowed). Eleven new QTLs were detected
in the subpopulations. There were significant interactions between the vrs1 and int-c loci for grain-protein percentage and S/T protein ratio. Results suggest that this mating of two different germplasm groups
caused a disruption of the balance of traits. Information on the number, position and effects of QTLs determining components
of malting quality may be useful for maintaining specific allele configurations that determine target quality profiles.
Received: 28 May 1999 / Accepted: 9 November 1999 相似文献
8.
Microbial invasion: a covert activity? 总被引:2,自引:0,他引:2
G L Gorby E N Robinson L R Barley C M Clemens Z A McGee 《Canadian journal of microbiology》1988,34(4):507-512
In contrast to nonpathogenic microorganisms that exist happily in biofilms on various organic and inorganic surfaces, many pathogenic microbes have the additional ability to invade host tissues by inducing their own endocytosis and transport across normally protective barriers. This phenomenon, designated "parasite-directed endocytosis," has been observed with a variety of surfaces (intestinal, genital, nasopharyngeal, and tracheal epithelium) as well as in endothelial cells. The mechanisms involved in invasion may involve a single factor as described for some species of Yersinia, or may require multiple factors as observed in Shigellae. For the majority of pathogens, the molecular mechanisms of invasion are not well understood (e.g., Neisseria gonorrhoeae). Because parasite-directed endocytosis is reminiscent of receptor-mediated endocytosis, it is quite possible that some pathogens engage in biologic mimicry by producing a molecule that resembles a natural host ligand, for which there is a host cell receptor. Such a masquerade may allow some microbes to enter the host's inner sanctum covertly in a manner analogous to the Trojan horse, rather than overtly by destroying the mucosa and entering host tissues directly. Whereas this hypothesis is speculative at present, bacteria that produce molecules resembling insulin, calmodulin, and chorionic gonadotropin have been described. 相似文献
9.
Levi N. Gray Anthony J. Barley David M. Hillis Carlos J. Pavn‐Vzquez Steven Poe Brittney A. White 《Ecology and evolution》2020,10(8):3738-3746
Sexually selected traits can be expected to increase in importance when the period of sexual behavior is constrained, such as in seasonally restricted breeders. Anolis lizard male dewlaps are classic examples of multifaceted signaling traits, with demonstrated intraspecific reproductive function reflected in courtship behavior. Fitch and Hillis found a correlation between dewlap size and seasonality in mainland Anolis using traditional statistical methods and suggested that seasonally restricted breeding seasons enhanced the differentiation of this signaling trait. Here, we present two tests of the Fitch–Hillis Hypothesis using new phylogenetic and morphological data sets for 44 species of Mexican Anolis. A significant relationship between dewlap size and seasonality is evident in phylogenetically uncorrected analyses but erodes once phylogeny is accounted for. This loss of strong statistical support for a relationship between a key aspect of dewlap morphology and seasonality also occurs within a species complex (A. sericeus group) that inhabits seasonal and aseasonal environments. Our results fail to support seasonality as a strong driver of evolution of Anolis dewlap size. We discuss the implications of our results and the difficulty of disentangling the strength of single mechanisms on trait evolution when multiple selection pressures are likely at play. 相似文献
10.
Barley K 《Journal of experimental botany》2004,55(399):1071-1078
Since the discovery of auxin, a debate has taken place as to whether the auxin distribution in elongating organs can account for the distinctive cell elongation profiles that have been found. In an attempt to address this important issue, the elongation profiles of cells have been compared in the hypocotyls of wild-type and auxin-hypersensitive axr3-1 Arabidopsis Columbia ecotype seedlings. Clear differences in cell elongation profiles were found in the two types of seedling, whether they were light- or dark-grown. However, it was not possible unambiguously to ascribe the cell elongation profile differences to the proposition that the axr3-1 mutation causes the hypocotyl to be hypersensitive to auxin. The possibility that the abnormal hypocotyl elongation profile of the mutant was a secondary effect, consequent on a more fundamental effect of the axr3-1 mutation, is considered. It is clear from this study that cell elongation and its control needs to be studied at the cell, and not the organ, level. To characterize a mutant as having a short, or long, hypocotyl is inadequate. To determine which factors control the timing and the magnitude of cell elongation requires the demonstration of correlations between the growth rate of cells and their content of regulating substances or their sensitivity to that substance. Studies of the cell elongation profiles of the many hypocotyl length mutants could also be a very effective means of probing the co-ordination of root and shoot elongation. 相似文献